1. Field of the Invention
The present invention relates to a thin film magnetic head employed in a magnetic disk drive and a magnetic tape storage system and the like. In particular, the invention relates to a thin film magnetic head comprising a magnetic yoke piece exposed at a medium-opposed surface adjacent a gap layer, and an upper or a lower magnetic yoke layer connected to the magnetic yoke piece, and to a method of producing the same.
2. Description of the Prior Art
Japanese Patent Laid-open No. 6-28626 discloses a well known thin film magnetic head comprising a lower front yoke layer swelling from the surface of the lower magnetic yoke layer toward the upper magnetic yoke layer, and an upper front yoke layer likewise swelling from the surface of the upper magnetic yoke layer toward the lower magnetic yoke layer. The upper and lower front yoke layers are designed to expose, at the medium-opposed surface or air bearing surface (ABS), tip ends narrower than that of the upper and lower magnetic yoke layers. Accordingly, the upper and lower front yoke layers are supposed to define a narrower write gap therebetween in the thin film magnetic head. The upper and lower front yoke layers are expected to achieve improvement in density of recording or data tracks on the magnetic recording medium such as a magnetic recording disk and a magnetic recording tape.
However, the aforementioned thin film magnetic head should accept extension of the upper magnetic yoke layer at the medium-opposed surface in the lateral direction of data track by a dimension wider than that of the upper front yoke layer. Accordingly, the thin film magnetic head usually suffers from a magnetic leakage from the protruding edges of the upper magnetic yoke layer at the medium-opposed surface. It has been revealed, contrary to expectation, that the aforementioned thin film magnetic head hardly contributes to reduction in width of a data track. Improvement in density of data tracks cannot thus be achieved.
It is accordingly an object of the present invention to provide a thin film magnetic head capable of reducing a magnetic leakage, obstructive to reduction in width of a data track, at a medium-opposed surface.
According to the present invention, there is provided a thin film magnetic head comprising: a magnetic yoke piece exposed at a medium-opposed surface adjacent a gap layer; a magnetic yoke layer connected to the magnetic yoke piece at a position retracting from the medium-opposed surface so as to expose its tip end at the medium-opposed surface; and a non-magnetic layer interposed between the tip end of the magnetic yoke layer and the magnetic yoke piece at the medium-opposed surface.
The non-magnetic layer serves to space apart the magnetic yoke piece and the tip end of the magnetic yoke layer from each other at the medium-opposed surface in the thin film magnetic head. The magnetic yoke layer can accordingly be kept away from the other magnetic yoke layer which is separated by the magnetic yoke piece and a gap layer, for example, from the magnetic yoke layer. It is possible to reduce a magnetic field directed to the magnetic yoke piece from the tip end of the magnetic yoke layer as well as a magnetic field directed to the other magnetic yoke layer from the edges of the magnetic yoke layer protruding in the lateral direction of a data track. Such magnetic fields from the magnetic yoke layer hardly induce magnetic reversal on a magnetic recording medium such as a magnetic recording disk or tape.
The magnetic yoke piece and the magnetic yoke layer may be an upper front yoke layer and an upper magnetic yoke layer of the thin film magnetic head. In this case, the tip end of the upper magnetic yoke layer can be spaced from the lower magnetic yoke layer which is separated by a gap layer from the upper front yoke layer and the upper magnetic yoke layer at the medium-opposed surface. It is possible to reduce a magnetic field directed to a magnetic recording medium from the edges of the upper magnetic yoke layer protruding in the lateral direction of a data track. Such magnetic field hardly induces magnetic reversal on the magnetic recording medium. A narrow magnetic field can reliably be defined by the upper front yoke layer narrower than the upper and lower magnetic yoke layers, so that the lateral width of a data track can be reduced.
A lower front yoke layer may also be formed to swell toward the upper front yoke layer along the medium-opposed surface from the surface o f the lower magnetic yoke layer. A narrower magnetic field can reliably be defined between the upper and lower front yoke layers both narrower than the upper and lower magnetic yoke layers. The lateral width of a data track can further be reduced.
A method of producing the aforementioned thin film magnetic head may comprise: forming a lower magnetic yoke layer on a surface of a wafer; forming an upper front yoke material layer extending rearward from a basic line above a surface of the lower magnetic yoke layer; forming a protection layer covering over the upper front yoke material layer; subjecting the protection layer to flattening process so as to expose the upper front yoke material layer; forming a resist covering over a rear end of the upper front yoke material layer so as to define a void pattern crossing the upper front yoke material layer along the basic line; depositing a non-magnetic layer within the void pattern in an electrolytic solution; and subjecting the wafer to grinding process along a plane including the basic line.
In general, it is difficult to form the upper magnetic yoke layer with its tip end retracting from the medium-opposed surface. When a photoresist is employed to define a void pattern corresponding to the shape of the upper magnetic yoke layer, for example, a developer hardly reaches a corner of the void pattern at the terminal end for defining the tip end of the upper magnetic yoke layer. The exposed photoresist cannot completely be washed out in the void pattern. Such void pattern only allows insufficient deposition for forming the tip end of the upper magnetic yoke layer in an electroplating process. The obtained upper magnetic yoke layer has a low dimensional accuracy.
On the other hand, when the void pattern is extended forward beyond the medium-opposed surface in forming the upper magnetic yoke layer, no corner is formed at the medium-opposed surface in the void pattern. It is accordingly possible to allow a developer to flow beyond the medium-opposed surface. The flow of a developer can be promoted. The exposed photoresist can completely be washed out in the void pattern corresponding to the tip end of the upper magnetic yoke layer. After the front end beyond the medium-opposed surface is cut off from the deposited upper magnetic yoke layer, the upper magnetic yoke layer of high dimensional accuracy can be obtained.
According to the aforementioned method, when the resist is removed after the deposition of the non-magnetic layer, the rear end of the upper front yoke material layer appears. The upper magnetic yoke layer is then formed to cover the rear end of the upper front yoke material layer and to extend forward beyond the basic line, so that the upper magnetic yoke layer can be formed with high dimensional accuracy in the vicinity of the basic line. In addition, when the medium-opposed surface is finally exposed after the grinding process, the non-magnetic layer serves to space the upper front yoke layer and the upper magnetic yoke layer from each other at the exposed medium-opposed surface, as described above. In this manner, the aforementioned thin film magnetic head can reliably be obtained. Moreover, management of the grinding amount in the grinding process may serve to control the depth of the non-magnetic layer spreading rearward from the medium-opposed surface.
Further, according to the method, a plane is defined to extend between the magnetic yoke piece and the magnetic yoke layer as a result of the flattening process to the protection layer. For example, an electric coil pattern may be formed on the plane. The plane allows the electric coil pattern to be designed finely. In addition, the plane also serves to achieve the formation of the non-magnetic layer with a high dimensional accuracy.
In realizing formation of the non-magnetic layer with a high dimensional accuracy, the void pattern is preferably provided with at least a stripe of an electrolytic solution passage extending along the basic line, and a pair of swelling reservoir connected to opposite ends of the electrolytic solution passage. Such void pattern may allow a developer, such as a tetramethylammonium hydroxide aqueous solution, to be smoothly introduced into the electrolytic solution passage from the swelling reservoir. It is accordingly possible to completely wash out the exposed resist within the narrow electrolytic solution passage. The void pattern can be formed with a high dimensional accuracy.
After the non-magnetic layer is formed in the above-described manner, the grinding process may be subjected to expose the medium-opposed surface. The thus obtained non-magnetic layer may comprise an interposed region extending on the plane in a lateral direction of a data track along the medium-opposed surface so as to define a predetermined depth from the medium-opposed surface, and a pair of extended regions connected to opposite ends of the interposed region so as to extend on the plane by a depth larger than the predetermined depth from the medium-opposed surface.
The aforementioned thin film magnetic head may be employed in combination with a magnetic read head such as a magnetoresistive (MR) sensor and a giant magnetoresistive (GMR) sensor. Not only a magnetic disk drive such as a hard disk drive (HDD) but also a magnetic tape storage system may employ the thin film magnetic head according to the present invention. Further, the thin film magnetic head may be supported not only on a flying head slider kept away from the surface of a magnetic recording medium, but also on a contact head slider comprising a medium-opposed surface which keeps contacting the surface of a magnetic recording medium.